Pickling solutions

ABSTRACT

THE PRESENT INVENTION PROVIDES AN ACID PICKLING SOLUTION CONTAINING A WETTING AGENT, THE SOLUTION ALSO CONTAINING AN ANTI-FOAMING AGENT CONDISTING ESSENTIALLY OF A MIXTURE OF OCTADECANEDIOL-1,12 AND A PARAFFIN OIL.

United States Patent O U.S. Cl. 252-143 4 Claims 7 ABSTRACT OF THE DISCLOSURE The present invention provides an acid pickling solution containing a wetting agent, the solution also containing an anti'foa'ming agent consisting essentially of a mixture of octadecaediol-l,12 and a paraffin oil.

BACKGROUND OF THE INVENTION The present invention relates to a process for preventing the formation of foam in acid pickling solutions which contain wetting agents and which are used mainly for the simultaneous pickling and cleaning of metal surfaces.

In order to allow pickling solutions to pickle and degrease simultaneously, wetting agents are added to the conventional pickling acids such as hydrochloric acid, sulfuric acid and phosphoric acid. Mixtures of wetting agents are also generally used, preferably non-ionic wet ting agents because of their higher solubility and better degreasing effect. Such non-ionic wetting agents are the products of addition of ethylene oxide to alkylphenols, optionally mixed with alkylbenzenesulfonates if required. The non-ionic wetting agents are known to foam only to a slight extent in the alkaline pH range, but they undergo considerable foam formation when used in an acid environment. Anionic active wetting agents, which foam to a considerable extent in the alkaline pH range because of their good solubility in that range, undergo only a slight foam development in the acid pH range. However, because of the limited solubility of the anionic compounds containing free sulfonic acid groups, these anionic active wetting agents can only be used to a limited extent and are furthermore less effective with respect to degreasing.

In order to prevent an excess formation of foam, antifoaming agents have to be added to the acid pickling solutions containing Wetting agents. This is particularly necessary when pickling is carried out at low temperatures, for example, when using hydrochloric acid as a pickling agent. Moreover an anti-foaming agent frequently has to be added to sulfuric acid pickling solutions containing Wetting agents and to phosphoric acid pickling solutions containing wetting agents which are frequently used at higher temperatures. The anti-foaming agents are added in order to prevent any considerable formation of foam when discharging these wetting agents containing solutions into a waste water treatment plant. The conventional anti-foaming agents for the neutral and alkaline pH ranges have proved to be ineffective in acid pickling solutions or have resulted in significant operating difiiculties during surface treatment processes such as galvanic treatment, which frequently follows pickling and degreasing. These troublesome influences can cause, for example, poor adhesion of the galvanic layer to the base metal.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a pickling solution and a pickling process whereby the formation of foam in acid pickling solutions, containing wetting agents, is substantially eliminated.

3,776,852 Patented Dec. 4, 1973 Other and further objects of the present invention will become apparent as the description thereof proceeds.

DESCRIPTION OF THE INVENTION The present invention is directed to an acid pickling solution comprising a pickling acid, a wetting agent, and an anti-foaming agent consisting essentially of a mixture of octadecanediol-l,l2 and a parafiin oil.

The present invention is also directed to a process for pickling metals wherein the improvement comprises contacting the metal with an acid pickling solution comprising a pickling acid, a wetting agent, and an anti-foaming agent consisting essentially of a mixture of octadecanediol-1,l2 and a parafiin oil for a time sufficient to effect pickling and degreasing.

The foam-inhibiting effect is obtained only by a mixture of the two substances, i.e. the formation of foam is not prevented solely by octadecanediol-1,12 or solely by paraffin oil. Similarly, other diols mixed with paraffin oil are virtually ineffective. Octadecanediol-l,12 and parafiin oil are generally present in the pickling solutions in the Weight ratio of 4:1 to 1:3.

The mixture of octadecanediol-LIZ and paraflin oil is added to the pickling solutions in a concentration of from 0.5% to 10.0% by weight based on the content of Wetting agent. It is to be recognized that the preferred concentration is dependent upon the wetting agent or mixture of wetting agents used, and upon the particular pickling acid.

Preferably, the diol/oil mixture of the present invention is added to the pickling solutions in a concentration of 0.05% to 2.0% by weight based on the acid concentration. Within this range, the most preferred concentration is again dependent upon the particular wetting agent or upon the mixture of wetting agents used, and upon the particular pickling acid.

The process has proved to be particularly advantageous if the mixture of octadecanedioll,l2 and paraffin oil is added to the pickling solutions in a concentration of from 0.1% to 1.2% by weight relative to the acid content, and from 1% to 7% by weight relative to the content of wetting agent.

Preferably, the parafiin oil is a refined mixture of hydrocarbons having a viscosity of to 200 cst. at 20 C.

In order to improve the cleaning eifect, the pickling solutions may additionally contain chlorohydrocarbons, preferably trichloroethylene.

When the process of the present invention is utilized, the formation of foam by a wetting agent additive is virtually completely prevented in acid pickling solutions. Adding octadecanediol-l,12 and paraflin oil to the pickling solutions has no negative effect on a subsequent surface treatment process, such as galvanizing. Undesirable foam development is also prevented when discharging the spent pickling solutions into the waste water system.

Essentially, the preferred pickling compositions of the invention comprise from about 5% to 25% ofa pickling acid selected from the group consisting of hydrochloric acid, sulfuric acid and phosphoric acid, from about 0.2% to 5% of a wetting agent selected from the group consisting of non-ionic surface active compounds, and mixtures of non-ionic surface active compounds and anionic surface active compounds, and a content of an anti-foaming agent consisting of a mixture of octadecanediol-l,12 and paraffin oil having a viscosity of between 100 and 200 cst. at 20 C., the weight ratio of said octadecanediol- 1,12 to said paraflin oil being between 4:1 to 1:3, said anti-foaming agent being present in an amount of from 0.5% to 10% by weight based on the amount of wetting agent and from 0.05% to 2% by weight based on the amount of pickling acid.

The non-ionic surface active compounds employed are alkylphenols having 6 to 12 carbon atoms in the alkyl, condensed with from 4 to 20 mols of ethylene oxide. The anionic surface active compounds employed are alkylbenzene-sulfonic acids having from 8 to 24 carbon atoms in the alkyl.

The pickling and degreasing process is conducted in the usual manner by contacting the surface of the metal, such as iron, steel, aluminum, etc. with a pickling composition of the invention at temperatures of from 15 C. to 80" C. for a period of about 1 second to about 5 minutes. Thereafter the metal surfaces are rinsed and dried.

The present invention will be further described with reference to the following specific examples which are not to be deemed limitive of the invention in any manner.

The percentages given in the examples refer to percentages by weight.

Example 1 0.01% octadecanediol-1,12 and 0.01% paraflin oil (150 cst.) were added to a 15% hydrochloric acid solution which contained 0.7% nonylphenol-l-IS E.O. (where 15 ED. means the product of addition of 15 moles of ethylene oxide to 1 mole of nonylphenol). The development of foam was determined at room temperature in accordance with DIN 53902, both with and without the addition of anti-foaming agent. The volume of foam was read off immediately after the foam had been produced at time equal to zero minutes and after 1 minute. 'In the absence of an anti-foaming agent, the volume of foam amounted to 600 ml. after minutes and 500 ml. after 1 minute; while the volume of foam amounted to 300 ml. after 0 minutes and 0 ml. after 1 minute with the above addition of octadecanediol-1,12 and paraflin oil.

Example 2 The following Tables 1 and 2 show the volumes of foam, according to DIN 53902, which were obtained when using a 15% hydrochloric acid solution having a content of 2.85% nonylphenol+9.5 ED. and 0.15% dodecylbenzene sulfonic acid at room temperature without an additive and with the addition of the given additive substances. The volume of foam was measured immediately after the foam had been produced at time equal to zero minutes and after minutes.

Table 1 shows the results obtained with octadecanediol-1,12, parafiin oil, and mixtures of these two substances. The time, after which the foam had completely decomposed with the additive in accordance with the in vention, is given in seconds.

4 The results of tests with mixtures of paraflin oil and other long-chain aliphatic hydroxyl compounds, and with known foam-suppressing products, are summarized in Table 2.

TABLE 2 15% E01 3 wetting agent=(2.85% nonylphenol 9.5 E.0. plus 0.15

' dodecylbenzene sulfonic acid) Volume of foam in ml. after- Addition 0 min. 5 min.

0.06% hexanediol-1,6 plus 0.12% B 650 500 0.06% decanediol-1,10 plus 0.12% B--." 650 500 0.12% 6-ethyldecanediol-3 5 plus 0.06% 750 580 0.12% nonadecanediol-Ll plus 0.06% B 700 510 0.04% 12-oxystearlc acid plus 0.04% 580 400 0.12% fatty alcohol (Cu-Cm) plus 0.06 o B.. 620 440 0.24% fatty alcohol (Cm-C13) plus 0 06 a B 550 420 0.12% ricinic alcohol plus 0.06% B 650 510 0.06% products of addition of- Ethylene oxide to polypropylene glycol (Pluronic L 101) plus 0.12% B 050 480 Propylene oxide and ethylene oxide to ethylene dlamine (Tetronic 701) plus 0.12% B...-.-.- 650 500 Ethylene oxide and propylene oxide to ethylene diamine plus 0.12% B. ...1 680 520 0.15% commercially available cold anti-foaming a ent 600 500 Example 3 2% nonylphenol+9.5 B0. and 0.1% dodecylbenzene sulfonic acid were added to a 15% hydrochloric acid solution to produce solution 1. In a further preparation, 0.02% octadecanediol-1,12 and 0.03% paraffin oil (140 cst.) were additionally added to a mixture having the components of solution 1 to produce solution 2. Solutions 1 and 2 were each diluted with water according to the volume ratio of 1:10 and of 1:100. Then the volume of foam were measured according to DIN 53902 and were compared at room temperature one minute after completion of the production of foam. In solution 2, the foam had completely decomposed in the two dilutions after one minute and the volume of foam was therefore 0 ml. However, with solution 1 one minute after completion a foam volume of 180 ml. was ascertained in the diluted solution of 1:10; and one minute after completion a foam volume of ml. was ascertained in the diluted solution of 1:100.

Example 4 1.4% nonylphenol+11 ED. and 0.06% alkylbenzene sulfonic acid were added to a 10% phosphoric acid solution to produce solution 1; and the volume of foam was ascertained, in accordance with DIN 53902 at room temperature. For comparison the volume of foam in a 10% phosphoric acid solution was determined after 0.035% octadecanediol-1,l2 and 0.035% parafiin oil cst.) had been added to the phosphoric acid solution in addition to the above-mentioned wetting agents to produce solution 2. In the case of solution 1, the volume of foam amounted to:

650 ml. at time equals zero minutes 560 ml. after 1 minute 520 ml. after 5 minutes In the case of solution 2, the volume of foam amounted to:

300 ml. at time equals zero minutes 20 ml. after 1 minute 10 ml. after 5 minutes Example 5 2.85 nonylphenol+11 E0. and 0.12% alkylbenzenesulfonic acid were added to a 20% sulfuric acid solution to produce solution 1; and the formation of foam was determined at room temperature in accordance with DIN 5 3902. The volume of foam was also measured after dilu tion with water in the volume ratio of 1:1 and of 1:100. These foam volumes of solution 1 were compared with the corresponding values of a 20% sulfuric acid solution to which a mixture of 2.85 nonylphenol+11 E.O., 0.12%

alkylbenzene-sulfonic acid, 0.04% octadecanediol-1,12 and 0.12% paraffin oil (170 cst.) had been added to produce solution 2.

TABLE 3 20% E 80 2.97% wetting agent=(2.85% nonylphenol plus 11 E.O. plus 0.12 alkylbenzenesulfonic acid) A solution containing 15% hydrochloric acid, 3.8% nonylphenol ll E.O., 0.2% dodecylbenzene sulfonic acid, 0.06% octadecanediol-1,12 and 0.06% paraflin oil (150 cst.) was used to remove rust and scale from steel parts at 18 to 25C. The spent pickling solution was diluted with water in the volume ratio of 1:50 and neutralised with sodium hydroxide solution. The pickling bath developed only negligible amounts of foam while working and upon dilution and neutralisation.

For the simultaneous pickling and degreasing of oil hardened steel parts at 40 to 60 C. a solution containing 20% sulfuric acid, 4.5% nonylphenol 9.5 E.O., 0.5% tetrapropylenebenzene sulfonic acid, 0.05% octadecanediol-l,12 and 0.15% paraffin oil (170 cst.) proved to be useful. The pickled steel parts could be electroplated thereafter without difficulties.

Aluminum parts contaminated with residues of polishing paste were degreased and pickled at 60 to 80 C. in a solution containing 5% phosphoric acid, 2% nonylphenol 9.5 E.O., 0.06% octadecanediol-l,l2 and 0.04% paraflin oil (120 cst.).

Although the present invention has been disclosed in connection with a few preferred embodiments thereof, variations and modifications may be resorted to by those skilled in the art without departing from the principles of the new invention. All of these variations and modifications are considered to be within the true spirit and scope of the present invention as disclosed in the foregoing description and defined by the appended claims.

We claim:

1. An aqueous pickling bath consisting essentially of from about 5% to 25% of a pickling acid selected from the group consisting of hydrochloric acid, sulfuric acid and phosphoric acid, from about 0.2% to 5% of a wetting agent selected from the group consisting of (a) an addition product of 4 to 20 moles ethylene oxide to 1 mole of alkylphenol having 6 to 12 carbon atoms in the alkyl,

and (b) the mixtures of said addition product of (a) with 5 an alkylbenzenesulfonate having 8 to 24 carbon atoms in the alkyl, and a content of an antifoaming agent consisting of a mixture of octadecanediol-l,12 and paraflin oil having a viscosity of between 100 and 200 cst. at 20 C., the weight ratio of said octadecanediol-1,12 to said parafiin oil being between 4:1 to 1:3, said anti-foaming agent being present in an amount of from 0.5% to 10% by weight based on the amount of wetting agent and from 0.05 to 2% by weight based on the amount of pickling acid.

2. The pickling solution as claimed in claim 1 in which the mixture of octadecanediol-l,l2 and parafiin oil is present in a concentration of from 0.1 to 1.2% by weight relative to the acid content and from 1 to 7% by Weight relative to the wetting agent content. 7 n

3. The aqueous pickling bath of claim 1, in which said wetting agent consists of from to by weight based upon the weight of said wetting agent of said addition product of (a) and from 0% to 5% by weight of said alkylbenzenesulfonate of (b) based upon the weight of said wetting agent.

4. A process for pickling metals in which the metals are treated with a solution consisting essentially of contacting the metal with an aqueous pickling bath consisting essentially of from about 5% to 25% of a pickling acid selected from the group consisting of hydrochloric acid, sulfuric acid and phosphoric acid, from about 0.2% to 5% of a wetting agent selected from the group consisting of (a) an addition product of 4 to 20 moles ethylene oxide to 1 mole of alkylphenol having 6 to 12 carbon atoms in the alkyl, and (b) the mixtures of said addition product of (a) with an alkylbenzenesulfonate having 8 to 24 carbon atoms in the alkyl, and a content of an antifoaming agent consisting of a mixture of octadecanediol- 1,12 and paraffin oil having a viscosity of between 100 and 200 cst. at 20 C., the weight ratio of said octadecanediol-1,12 to said paraflin oil being between 4:1 to 1:3, said anti-foaming agent being present in an amount of from 0.5% to 10% by weight based on the amount of wetting agent and from 0.05% to 2% by weight based on the amount of pickling acid.

References Cited UNITED STATES PATENTS 2,085,709 6/1937 Steibelt 252-321 X 2,987,425 6/ 1961 Shaw 252143 X 3,650,964 3/ 1972 Sedliar et a1 252-143 X FOREIGN PATENTS 710,080 6/1954 Great Britain 252-32l X LEON D. ROSDOL, Primary Examiner H. A. PITLICK, Assistant Examiner US. Cl. X.R. 

